Hydraulic bending press

ABSTRACT

A hydraulic press for bending plates and the like, is disclosed having a single-acting hydraulic pressing cylinder. A plurality of plunger pumps feed hydraulic fluid of a lower pressure and higher supply rate to the hydraulic pressing cylinder to enhance the speed of the ram during the approach thereof to the partner tool or while a light load is applied. Fluid of a higher pressure and lower supply rate is provided to the pressing cylinder to retard and empower the ram when a heavy load is applied, e.g., after the start of the bending operation.

United States Patent [191 Hamarla [451 Uct.,i97d

[ HYDRAULIC BENDING PRESS [76] inventor: Teruma Hamada, 18-402, 13,

3-chome Kitakarasuyama, Setagaya-ku, Tokyo, Japan [22] Filed: July 11,1972 [21] Appl. No: 270,646 1 Related U.S. Application Data [63]Continuation-impart of Ser. No. 75,566, Sept. 25,

1970, abandoned.

[30] Foreign Application Priority Data Oct. 13, 1969 Japan 44-81167 52use]. ..72/443,72/453, 100/269R 51 in o: B2lj9/l2 [58] FieldofSearch..72/4s3,3s9,443;

IOU/269R [56] References Cited UNITED STATES PATENTS 846,266 3/1907 VonPhilp 100/269 R 3,081,659 3/1963 Theobald 100/269 R PrimaryExaminer-Charles W. Lanham Assistant Examiner-*Gene P. Crosby Attorney,Agent, or Firm-Cecily L. Frey 57 ABSTRACT A hydraulic press for bendingplates and the like, is disclosed having a single-acting hydraulicpressing cylinder. A plurality of plunger pumps feed hydraulic fluid ofa lower pressure and higher supply rate to the hydraulic pressingcylinder to enhance the speed of the ram during the approach thereof tothe partner tool or while a light load is applied. Fluid of a higherpressure and lower supply rate is provided to the pressing cylinder toretard and empower the ram when a heavy load is applied, e.g., after thestart of the bending operation.

1 Claim, 2 Drawing Figures PATENTEU 8 74 SHEEI 2 0F 2 l nvnnAuLicsnunrno mass DESCRIPTION OF THE INVENTION The present invention relatesto a press brake or socalled bending press, characterized in that one ofthe upper and lower aprons is designed to rise or fall through theaction of a single-acting hydraulic pressing cylinder, and the returnmovement of the apron is effected by an accumulator or by the aprons owngravity. Plural plunger pumps of the same small shape are adapted to bedriven in different shifted phases by a crank shaft or swash discs, inthat a first hydraulic cylinder of a first one of the plunger pumps isconnected with a fluid path to the pressing cylinder for actuating theapron through a check valve while one end of another fluid path, fromanother hydraulic cylinder of a second one of the plunger pumps, or of afluid path from each hydraulic cylinder, is connected with thefirst-named fluid path to the pressing cylinder, for actuating the oneapron through a lower-pressure check valve so as to permit hydraulicfluid to flow from the first cylinder. The other end of the second-namedfluid path is connected with a drain circuit through a higherpressurecheck valve, and the single-acting pressing cylinder receives the fluidat a lower pressure and higher supply rate, to work at a higher speed,when the apron is lightly loaded, e.g., when approaching to squeezeplate materials between the upper and lower molds. The same pressingcylinder receives the fluid at a higher pressure and lower supply rate,to work at a lower speed, when the one apron is heavily loaded, e.g.,for processing the work materials.

The object of the present invention is to provide a hydraulic bendingpress having the above-mentioned mechanism and presenting desirablefunctions such that said hydraulic means provides a larger pressure onthe latter because said mobile apron receives a larger load at thebeginning of the work process, and'said hydraulic means is automaticallycontrolled to obtain a high supply rate so as to transfer as quickly aspossible when being loaded only with the weight of the mobile apronapproaching the upper and the lower molds before the beginning of thework process or only with the resistance of inserting forcedly into theaccumulator.

For this purpose, larger machines may resort to the system of feedinghydraulic fluid or oil while approaching one hydraulic cylinder disposedat the center of gravity without load and of collecting the oil supplyfrom plural surrounding hydraulic cylinders after the start of thebending operation. However, smaller machines having a single cylindercannot adopt such a mechanism.

On the other hand, the category of a single cylinder type includes aconventional system having one pump of a higher pressure and lowersupply rate together with two pumps of a lower pressure and highersupply rate, wherein said pumps are changed over, one with the other.This system, however, is complicate in its mechanism and isdisadvantageous in requiring switch-over manipulation. Also theproduction cost is rather high.

A bending press having the above-described mecha nism of the presentinvention carries out automatically a lower-pressure and high-speedoperation while being loaded on the mobile apron, and a higher-pressureand lower-speed operation while being highly loaded. In particular, sucha bending press can automatically be switched over between ahigher-pressure lower-speed operation when requiring higher loading, anda lowerpressure higher-speed operation when requiring only lowerloading, according to different work materials.

An exemplary embodiment will be described in detail, for an exemplaryarrangement employing three hydraulic pumps, with reference to theattached drawings, wherein FIG. 1 is a front view of an exemplarybending press; and

FIG. 2. is a partly schematic showing of hydraulic means for the bendingpress of FIG. 1 of the present invention.

In the bending press as shown in FlG. 11, K denotes a stationary apronand R denotes a mobile apron which can conduct the work process in itselevated position and is free from loading in its bottom position. Vdenotes a hydraulic pressing cylinder mechanism for driving the mobileapron R.

In FIG. 2, a single-acting hydraulic cylinder mechanism V includes apiston Pv for lifting and dropping the mobile apron R. 0 denotes a shaftdriven bya motor M; A, B and C denote hydraulic cylinders of plungerpumps of which respective and cooperative pistons la, Pb and Fe engageshaft Q at connections Qa, Oh and Qc. T denotes hydraulic fluid or oiltanks (which may be in the form of a single tank, D1, D2, D3, D4, D5,D6, D7, D8 and D9 denote check valves; Sll, S2, S3, S4, S5, S6, S7, S8and S9 denote springs for the check valves; G denotes a fluid feedingtube for the hydraulic working cylinder V of the mobile apron; numeralsi to 24 denote various fluid paths.

In the mentioned constructions, the spring S9 is more powerful than thespring S6, and D6 denotes a low pressure check valve. Valve D6, with itsappropriate spring S6, is disposed between fluid path sections 6, 7. D8,a relief check valve, is designed to relase hydraulic fluid at themaximum pressure obtained when a work material plate is squeezed betweenthe upper and lower,

molds at the end of the bending process and prevents these molds fromapproaching each other. in this manner, D8 prevents any damages of otherhydraulic members and naturally works with a pressure higher than thatof D9. D9 is formed as a high pressure check valve.

Preferably, as shown, fluid paths i9, 23 are connected to tank T by wayof valve D8, having spring SS, between fluidpath sections 20, 211.Springs Sil to S5, S7 are of course for the respective valves Dl to DSand D7, respectively. Valves Dll, D2 and DS are flanked (with theirsprings) by the respective fluid path sections 2, 3; 9, 24; and 115,116.

Now that the construction of the bending press has been described, thefunction thereof will be explained. When the hydraulic cylinders A, Band C for respective plunger pumps are in the fluid feeding stroke, thecylinder C works to close the check valve D1, while the pressure fluidin the hydraulic cylinder C opens the check valve Dz through fluid pathsl, 4 and is introduced in path 13 through paths 5 H. The hydrauliccylinder similarly works to close the check valve D3, open the checkvalve D4 through paths 6, lit) and is introduced in path 13 through oilpath 111.. Then this fluid supply is added to the pressure fluid of thehydraulic cylinder C in path 13 to open the low pressure check valve D6and is introduced into supply tube G through paths 19, 22 and 23.

On the other hand, the high pressure check valve D9 closes to interruptthe flow through path 7. Furthermore, during the fluid feeding stroke ofthe hydraulic cylinder A, the pressure fluid closes the check valve Dand opens the check valve D7 through paths 14, 117 thus flowing throughpaths 18, 23 toward oil supply tube G together with the pressure fluidfrom the hydraulic cylinders B and C.

All this while, the high pressure check valve D9 remains closed. It isnoted that, when the working portion of the rising mobile apronapproaches the working portion of the stationary apron without effectingany operation, the pressure fluid supplied from the hydraulic cylindersA, B and C is incorporated to work as its entire mass so as to form acondition of low pressure and high supply rate, thus causing the workingapron to rise rapidly.

When the working apron begins to press a work material, the work loadincreases rapidly to involve a pressure increase inside fluid path 23,thus closing the check valve D6 so that the pressure fluid from thehydraulic cylinders B, C opens the valves D2, D4, D9 and returns intoone of the tanks T, relatively without resistance. Thus a large workingload is not required.

In this manner, as the working load of all the pumps or the output powerof 'motor M concentrates exclusively into the hydraulic cylinder A, thecondition of high pressure and low supply rate is established so thatthe mobile apron may work large power.

When the bending operation is finished, a changeover valve Y is turnedto connect the fluid supply tube G and path 23 with a discharge circuit.In this case, the mobile apron begins to rise or fall by its own gravityor by the effect of an accumulator and so the upper and lower moldsseparate to resume their initial positions. The pressure from thecylinder A of the plunger pump is discharged through path 14, 23 and thechange-over valve Y, while all the pressure fluid from the cylinders B,C is discharged through paths 22, 23 and changeover valve Y afterpassing the check valve D6 because the spring S6 is less powerful thanthe spring S9, as explained before. The operation of the bending pressis at a slow speed and with a i always started by changing over thevalve Y to connect the fluid supply tube G with path 23.

As described hereinbefore, the bending press of the present invention isconstructed in the manner that the motor and the plunger pump arecontinuously rotated, and the simple manipulation of the change-overvalve permits the working apron to automatically move at a higher speedin the case of requiring smaller load for the approach of the upper andlower molds, and to move at a lower speed, in the case of requiring aheavier load for the actual bending process. The invention, therefore,offers such a simple and sure structure of bending press in a compactform.

I claim:

, 1. A hydraulic press for bending plates and the like, comprising, incombination, an upper and a lower apron, one of said aprons beingdesigned selectively to rise and to fall by the action of asingle-acting hydraulic pressing cylinder, return movement of said oneapron being effected by the apron s own gravity, a plurality of plungerpumps driven in different shifted phases alternatively byrespectiveswash discs, a first hydraulic cylinder of the first one of said plungerpumps connected with a'first fluid path to said pressing cylinder foractuating said one apron through a check valve while one end of a secondfluid path, from a second hydraulic cylinder of the second one of saidplunger pumps is connected with said first fluid path to said pressingcylinder, for actuating said one apron through a lowerpressure checkvalve so as to permit hydraulic fluid to flow from said first cylinder,the other end of said second fluid path being connected with a draincircuit through a higher-pressure check valve, the workingcharacteristics of said one apron being changed over so that, in thecase of said one apron being loaded lightly such as for approaching oneof upper and lower molds, said one apron works with a lower pressure anda higher supply rate, whereas in the case of said one apron starting thepress work, the fluid supply from said second cylinder is dischargedwithout noteworthy resistance, and only the fluid supply from said firstcylinder is introduced into said pressing cylinder so that said oneapron works with a higher pressure and a lower supply rate.

1. A hydraulic press for bending plates and the like, comprising, incombination, an upper and a lower apron, one of said aprons beingdesigned selectively to rise and to fall by the action of asingle-acting hydraulic pressing cylinder, return movement of said oneapron being effected by the apron''s own gravity, a plurality of plungerpumps driven in different shifted phases alternatively by respectiveswash discs, a first hydraulic cylinder of the first one of said plungerpumps connected with a first fluid path to said pressing cylinder foractuating said one apron through a check valve while one end of a secondfluid path, from a second hydraulic cylinder of the second one of saidplunger pumps is connected with said first fluid path to said pressingcylinder, for actuating said one apron through a lowerpressure checkvalve so as to permit hydraulic fluid to flow from said first cylinder,the other end of said second fluid path being connected with a draincircuit through a higher-pressure check valve, the workingcharacteristics of said one apron being changed over so that, in thecasE of said one apron being loaded lightly such as for approaching oneof upper and lower molds, said one apron works with a lower pressure anda higher supply rate, whereas in the case of said one apron starting thepress work, the fluid supply from said second cylinder is dischargedwithout noteworthy resistance, and only the fluid supply from said firstcylinder is introduced into said pressing cylinder so that said oneapron works with a high pressure and a lower supply rate.